UNIVERSITY    OF    CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT   STATION 

BERKELEY,    CALIFORNIA 


PLANTING  AND  THINNING 

DISTANCES  FOR  DECIDUOUS 

FRUIT  TREES 


F.  W.  ALLEN 


BULLETIN  414 

November,  1926 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1926 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/plantingthinning414alle 


PLANTING  AND  THINNING  DISTANCES  FOR 
DECIDUOUS  FRUIT  TREES 


F.  W.  ALLENi 


INTRODUCTION 

In  planting  an  orchard,  one  of  the  first  questions  to  be  settled  is 
the  amount  of  space  to  be  allotted  to  each  tree  for  root  and  top 
development.  This  requires  a  decision  as  to  how  far  apart  the  rows 
shall  be  and  the  distance  between  the  trees  in  the  rows.  Aside  from 
the  number  of  trees  that  can  be  safely  planted  on  an  acre  of  ground, 
certain  other  practical  considerations  enter  in,  such  as  the  best 
arrangement  of  the  trees  for  convenience  in  cultivating,  irrigating, 
brush  burning,  spraying  and  harvesting.  A  closely  related  problem 
is  the  question  of  what  shall  be  done  with  orchards  that  are  found 
to  be  too  closely  planted.  In  the  first  instance  the  planter  strives  to 
avoid  a  mistake,  while  in  the  second  he  tries  to  correct  one.  Both 
topics  will  be  discussed  in  the  succeeding  pages. 

The  information  on  which  this  discussion  is  based  was  secured  from 
an  orchard  planted  on  the  University  Farm  at  Davis  for  the  purpose 
of  studying  planting  distances,  and  from  careful  observations  made 
in  a  number  of  established  orchards  in  different  parts  of  the  state. 

EXPERIMENTAL    ORCHARD    AT    DAVIS 

The  experimental  orchard  at  Davis  was  planted  in  February,  1915, 
and  consisted  of  the  following  fruits :  Royal  apricots,  Climax  and 
Pond  plums,  Bartlett  pears,  Royal  Ann  cherries,  Elberta  peaches, 
and  French  prunes,  the  trees  being  arranged  in  blocks,  with  each 
block  representing  a  different  planting  distance.  The  planting  dis- 
tances ranged  from  12  x  12  feet  to  36  x  36  feet,  the  number  of  trees 
per  block  varying  from  302  in  the  former  instance  to  only  33  in  the 
latter.  The  total  number  of  trees  planted  was  668,  but  as  each  block 
was  provided  with  guard  rows  so  that  all  trees  used  for  record 
purposes  were  surrounded  with  other  trees  of  their  kind,  only  354 
remained  on  which  to  keep  growth  and  yield  data.  Table  1  shows 
the  number  of  trees  in  each  block. 

This  orchard  was  valuable  chiefly  for  studying  the  comparative 
growth  of  trees  under  various  conditions  of  planting,  ranging  from 


1  Assistant  Pomologist  in  the  Experiment  Station. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE   1 

Planting  Plan  and  Number  of  Trees  of  Each   Fruit  Planted  in 

Different  Blocks 


Planting  distance  and 
kind  of  fruit 

Number 
of  trees 
planted 

Number 

used  for 

record 

purposes 

Planting  distance  and 
kind  of  fruit 

Number 
of  trees 
planted 

Number 

used  for 

record 

purposes 

12x12  feet: 

45 
25 
25 
45 
36 
36 
40 

24 
16 
12 
24 
24 
28 
24 

15 
9 
9 

15 
15 
18 
15 

24 
12 
12 
24 
24 
24 
24 

15 
9 
6 
15 
15 
15 
15 

8 
4 
4 

8 
8 
8 
8 

24x24  feet: 

Apricot 

Plum  (Japanese) 

Plum  (European) 

Pear 

12 
6 
9 

12 
12 
15 
12 

9 
6 
6 
9 
9 

12 
9 

9 

12 
9 

6 

2 

4 

6 

Peach 

6 

6 

Prune 

6 

16x16  feet: 

Apricot 

30x30  feet: 

Apricot 

Plum  (Japanese) 

Plum  (European) 

Pear 

4 
2 

Plum  (European) 

Pear 

,      2 
4 

4 

4 

4 

20x20  feet: 

Apricot 

36x36  feet: 

Apricot 

4 
4 

4 

Pear 

a  badly  crowded  condition  to  the  opposite  extreme  where  they  were 
so  far  apart  that  there  could  be  little  or  no  competition  for  moisture, 
soil  nutrients,  or  light.  Unfortunately,  the  plans  made  by  the  orig- 
inator of  the  experiment  did  not  provide  for  as  many  trees  in  the 
widely  planted  blocks  as  there  should  have  been.  Through  the  vicissi- 
tudes of  subnormal  rainfall  and  shortage  of  water  for  irrigation 
purposes  during  two  or  three  seasons  when  the  trees  were  coming 
into  bearing,  it  became  apparent  that  those  in  the  crowded  blocks 
in  particular  were  being  subjected  to  unusually  severe  conditions  and 
that  they  were  suffering  accordingly.  Radical  thinning  by  taking  out 
trees  was  resorted  to,  but  the  apricots  and  peaches  did  not  recover 
their  lost  vigor.  Even  those  having  plenty  of  room  showed  continued 
signs  of  drought  injury. 

Incidentally,  this  experiment  taught  two  lessons:  First,  that  it 
is  hazardous  to  allow  young  trees  to  suffer  for  water  to  the  extent 
of  slowing  down  their  growth  and,  second,  that  certain  trees,  at  least, 
do  not  recover  after  once  having  been  injured  from  overcrowding 
during  a  period  of  dry  years. 


BUL.  414]      PLANTING    DISTANCES    FOR    DECIDUOUS    FRUIT    TREES 


FACTORS    INFLUENCING    PLANTING    DISTANCES 

Horticultural  writers  have  not  always  been  uniform  in  their 
advice  as  to  the  amount  of  space  trees  should  be  allowed  or  as  to 
their  exact  arrangement  in  the  orchard.  Even  experienced  fruit 
growers  in  a  limited  district  may  not  be  entirely  in  agreement  as  to 
how  the  trees  should  be  spaced  or  the  total  number  that  may  be 
allowed  to  the  acre.  There  are  certain  basic  considerations  which 
need  to  be  taken  into  account  in  deciding  planting  distances. 

Even  under  best  conditions  for  normal  growth  not  all  fruit  trees 
attain  the  same  size  at  maturity;  moreover,  growth  habits  of  the 
different  species  and  varieties  as  to  size  and  shape  are  quite  varied. 
Some  are  normally  tall  and  slender,  at  least  for  many  years,  while 
others  are  spreading  in  their  habit  of  growth  from  the  beginning. 
Sweet  cherries,  for  example,  in  good  soils  often  attain  a  height  of 
thirty-five  feet  and  a  branch  spread  of  perhaps  twenty  feet ;  while 
sour  cherries  are  rarely  over  twenty  feet  high  and  have  a  branch 
spread  not  exceeding  twelve  or  fifteen  feet.  Pears  are  noted  for 
being  upright  in  their  growth,  while  apples  and  apricots  are  generally 
wide-spreading.  Some  trees  when  grown  on  certain  rootstocks  such 
as  the  Bartlett  pear  on  the  quince  are  also,  normally,  dwarfs. 

The  soil,  whether  deep  or  shallow,  has  much  to  do  with  the  size 
of  a  tree  of  a  given  species  or  variety.  On  shallow  soil  even  trees 
that  are  normally  large,  if  they  survive,  are  apt  to  be  small.  However, 
on  such  soils  where  the  roots  are  unable  to  penetrate  deeply,  they  are 
apt  to  range  widely  in  search  of  both  food  and  moisture  so  that  trees 
should  not  be  unduly  crowded  simply  because  it  is  known  that  they 
will  not  attain  large  size. 

The  moisture  supply  in  the  soil  is  perhaps  the  most  important 
single  factor  affecting  the  growth  of  fruit  trees.  Even  on  the  most 
productive  soils,  trees  will  make  a  small  growth,  soon  lose  their 
vitality,  and  gradually  die  if  allowed  to  suffer  for  water.  Evidence 
of  this  has  been  noted  in  non-irrigated  orchards,  especially  those  where 
small  fruits  are  interplanted  between  the  trees. 

Tree  sizes  can  be  regulated  to  a  considerable  degree  by  pruning. 
Heavy  annual  pruning  consisting  of  shearing  back  the  new  growth 
tends  to  keep  the  trees  small.  This  type  of  pruning  may  adapt  them 
to  certain  planting  distances,  whereas  if  they  were  handled  by  the 
so-called  "long  pruning,"  they  would  inevitably  require  more  space. 
There  are  really  two  considerations :  the  welfare  of  the  roots  as  regards 
a  proper  moisture  supply,  and  the  welfare  of  the  tops.     If  unduly 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


crowded,  the  tops  may  not  secure  the  necessary  amount  of  sunlight ; 
moreover,  harvesting,  spraying,  and  other  field  operations  may  be 
hampered.  Hoot  growth,  too,  is  influenced  by  heavy  pruning.2  Heavy 
shearing  of  the  branches  annually  tends  to  restrict  the  growth  of  the 
roots. 

Again,  the  purpose  of  the  orchard  may  have  an  influence  on  the 
spacing  of  the  trees.  Most  orchards  are  planted  with  the  idea  that 
the  trees  are  to  be  permanent  and  hence  they  should  be  given  a  suffi- 
cient amount  of  space  for  the  best  development  of  both  tops  and 
roots  over  a  long  period  of  years.  Under  certain  circumstances  it  may 
seem  necessary  to  plant  a  temporary  orchard  in  which  the  trees  may 
be  set  very  thickly.  They  are  brought  into  bearing  early  and  given 
little  or  no  pruning  in  order  to  secure  a  few  heavy  crops ;  then,  when 
their  vigor  begins  to  decline,  all  are  removed  from  the  land.  In  times 
of  high  prices  for  a  certain  fruit  it  may  be  good  business  to  give  the 
trees  a  reasonable  amount  of  space  in  which  to  develop  but  yet  plant 
the  maximum  number  of  trees  to  the  acre.  Such  growers,  of  course, 
should  be  willing  to  take  the  risk  of  injuring  the  trees  by  slight  crowd- 
ing. The  returns  from  the  orchard  may  justify  this  procedure, 
although  the  orchards  should  be  regarded  as  only  semi-permanent. 

A  single  adverse  season  as  regards  water  supply  may  result  in 
severe  or  fatal  injury  to  a  high  percentage  of  such  trees,  whereas 
under  favorable  conditions  of  moisture  and  with  first  class  cultural 
attention  they  may  survive  and  be  useful  for  many  years. 

Table  2  may  be  useful  in  computing  the  number  of  trees  required 
for  any  given  area. 

TABLE  2 

Number,  of  Trees  Eequired  per  Acre 


Planting  distances, 
in  feet 

Number  of  trees  per 
acre  square  or  alter- 
nate planting* 

18x18 

134 

20x20 

108 

22x22 

90 

25x25 

70 

27x27 

59 

30x30 

48 

35x35 

35 

40x40 

27 

50x50 

17 

60x60 

12 

*  Figures  are  exact  only  for  a  multiple  of  acres.     For  hexagonal  planting  add  15  per  cent  to  above 
figures;  for  quincunx  planting  add  100  per  cent. 


2  Chandler,  W.  H.    Eesults  of  some  experiments  in  pruning  fruit  trees.     Cornell 
Univ.  Agr.  Exp.  Sta.  Bui.  415:5-8.     1923. 


BuL.  414]      PLANTING   DISTANCES   FOR   DECIDUOUS   FRUIT    TREES 


RELATION     OF     PLANTING     DISTANCES     TO     THE     GROWTH      AND 
FRUITING   OF  THE  TREES 

Tree  growth. — The  accompanying  chart,  figure  1,  illustrates  the 
total  size  of  the  experimental  trees  on  the  University  Farm  and  also 
the  annual  rate  of  growth  as  measured  by  increase  in  trunk  diameter. 
During  the  first  three  years  after  planting,  differences  in  growth 
between  the  trees  planted  at  12  feet  and  those  planted  at  30  or  36 
feet  apart  are  small  and  of  no  special  significance.  The  fourth  season, 
1918,  being  unfavorable  on  account  of  only  ten  inches  of  rainfall 
between  September,  1917,  and  September,  1918,  and  no  irrigation 
water  available,  all  trees  made  less  growth  than  either  the  year  pre- 
vious or  the  one  following.  At  this  time  the  apricots  and  peaches 
planted  at  the  wider  distances  were  of  decidedly  larger  size.  During 
1919  all  trees  made  a  uniform  gain  except  the  apricots  which  again 
made  a  relatively  small  amount  of  growth  in  the  closely  planted  blocks. 
Beginning  with  1920,  another  dry  season,  the  dwarfing  effects  of  close 
planting  were  even  more  apparent.3  It  will  be  noted  that  the  effects 
of  the  varying  distances  were  much  more  marked  with  the  apricot, 
peach,  and  cherry  than  with  the  plum,  prune,  and  pear.  The  growth 
for  the  pear  is  particularly  uniform  in  each  of  the  planting  distances 
during  the  entire  ten-year  period. 

The  relative  amount  of  space  available  for  the  development  of  the 
tree-top  or  spread  of  branches  has  been  correspondingly  striking. 
Peaches  and  apricots,  naturally  of  a  spreading  habit,  were  by  1918 
in  the  closer  planted  blocks  being  forced  into  a  smaller,  more  upright 
habit  of  growth,  as  illustrated  in  figure  2  and  figure  5A.  The  amount 
and  vigor  of  the  new  wood  produced  also  gradually  became  less  until 
1922,  when,  in  a  much  weakened  condition,  50  per  cent  of  the  trees 
were  removed.  Although  to  a  somewhat  lesser  extent  plums,  prunes, 
and  cherries  were  likewise  influenced  under  similar  conditions,  and 
thinning  was  also  necessary  in  order  to  prevent  the  gradual  dying  of 
the  trees.  Pears,  naturally  of  an  upright  habit,  have  been  the  least 
affected  in  the  character  of  their  growth.  Crowding  has  produced 
smaller  and  perhaps  slightly  weaker  trees,  but  the  general  character 
of  growth  has  been  little  influenced. 

Fruiting  habits. — As  the  branches  of  the  peach  and  apricot  when 
crowded  were  forced  upward  to  secure  sunlight,  the  new  wood  bearing 
all  the  fruit  of  the  peach  and  a  portion  of  that  in  the  apricot  became 
more  limited  and  higher  up  in  the  tree.     With  a  gradual  dying  of 


s  Increase  in  size  of  trees  planted  at  12  and  16  feet  during  and  after  1922, 
primarily  the  result  of  thinning. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


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Fig.   1. — Average  annual  and  total  trunk  diameter  growth  of  trees  at   different 

planting   distances. 


BUL.  414]      PLANTING   DISTANCES   FOR   DECIDUOUS   FRUIT    TREES  9 

the  older  bearing  surface  on  the  lower  branches  the  subsequent  crops 
were  reduced.  Trees  producing  their  fruit  primarily  on  spurs  or 
having  a  natural,  upright  habit  of  growth,  were  little  influenced  in 
their  fruiting  habits. 


Fig.  2. — Elberta  peach  trees  12  x  12  feet  apart.  Photographed  in  1922  before 
thinning.  Very  upright  growth  of  branches  with  little  fruiting  wood  except  in 
the  tops  of  the  trees. 


10 


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Yields. — Both  frost  and  lack  of  adequate  irrigation  reduced  the 
yields  of  the  trees  under  experiment  to  such  an  extent  as  to  make 
them  scarcely  comparable  with  yields  in  many  commercial  districts. 
However,  the  yields  of  the  different  plots  are  comparable  and  a 
few  very  significant  facts  are  brought  out  by  the  records  secured. 
Table  3  shows  weights  of  fruit  secured,  while  figure  3  shows  the 
same  data  in  diagrammatic  form. 


TABLE  3 
Fruit  Yields  Per  Acre — 1918-1925 


Plant- 
ing dis- 
tance, 
feet 

Num- 
ber of 
trees  to 
the  acre 

Annual  yield  in  pounds  to  the  acre 

Trees 

1918 

1919 

1920 

1921 

1922 

1923 

1924 

1925 

2,340 
4,250 
7,938 
10,125 
8,040 
3,782 

Total 

Royal  apricots 

12x12 
16x16 
20x20 
24x24 
30x30 
36x36 

302 
170 
108 
75 
48 
33 

322 
119 

3,865 
3,196 
2,528 
2,010 
2,476 
1,132 

19,751 
7,922 
4,622 
6,277 
3,945 
3,484 

No 
crop 

4,432* 
5,333f 
11,253 
10,237 

7,780 
7,375 

2,703 
3,876 
4,978 
600 
590 
3,171 

3,722 
2,422 
270 
1,071 
1,761 
6,448 

37,145 
27,118 
31,589 
30,320 
24,606 
25,392 

14 

Climax  plums 

12  x  12 
16x16 
20x20 
24x24 
30x30 
36x36 

302 
170 
108 
75 
48 
33 

1,540 
1,360 

712 
52 

465 

4,167 
2,176 
2,170 
1,012 
681 

9,633 
8,959 
6,589 
3,915 
2,313 

No 
crop 

15,462 
9,775 
11,016 
13,125 
6,081 
No  tr 

3,9561 
6,120 
9,450 
7,770 
9,168 
ees 

1,939 
1,054 
1,404 

3,787 
1,636 

4,620 
2,397 
2,775 
5,475 
2,001 

41,317 
31,841 
34,116 
35,136 
22,345 

12  x  12 

16x16 
20x20 
24x24 
30x30 
36x36 

302 
170 
108 

75 
48 
33 

543 
255 
194 

3,926 
6,137 
4,708 
727 
1,752 

No 
crop 

9,483 
7,242 
5,400 
420 
312 
Notr 

No 
data 

ees 

No 
crop 

3,382 
3,910 
2,754 
3,750 
4,200 

17,334 

17,544 

13,056 

- 

4,897 

105 

6,369 

Bartlett  pears 

12  x  12 
16x16 
20x20 
24x24 
30x30 
36x36 

302 
170 
108 
75 
48 
33 

2,506 

680 
648 
150 
62 
613 

2,657 

1,139 

928 

285 

729 

1,359 

No 
crop 

11,476 

6,749 
6,815 
5,310 
7,752 
2,614 

10,479 
2,091 
5,400 
5,332 
8,208 
4,494 

33 

714 

356 

3,825 

3,504 

4,851 

1,700 
6,493 
4,060 
14,700 
14,640 

27,151 

17 
10 

11,390 

1,944 

840 

3,043 

1,821 

16,101 
15,742 

23,298 

3 

15,755 

12  x  12 
16x16 
20x20 
24x24 
30x30 
36x36 

302 
170 
108 
75 
48 
33 

120 

1,683 

21 

52 
14 

1,087 
850 
4,978 
4,125 
3,062 

No 
crop 

No 
crop 

2,907 

782 
2,581 
10,185 
7,636 

396f 

7,214 

20,850 

21,216 

No  tr 

10,204 

18,854 

637 
16,857 
ees 

50,549 
63,425 

12x12 
16  x  16 
20x20 
24x24 
30x30 
36x36 

302 
170 
108 
75 
48 
33 

3,050 

1,037 

291 

217 

163 

6,432 
5,321 
2,149 
1,597 
446 

No 
crop 

4,983 
2,004 
4,212 
1,147 
1,003 
Notr 

2,174t 
10,574 
19,332 
14,612 
10,171 
ees 

No 
crop 

985 
2,805 
5,400 

7,695 
6,240 

17,624 

21,741 

31,384 

25,268 

18,023 

*  Trees  thinned  from  302  to  the  acre  to  75.5  to  the  acre  leaving  only  one-fourth  of  the  original  planting . 
t  Trees  thinned  from  170  to  the  acre  to  85  to  the  acre,  leaving  only  one-half  of  the  original  planting. 
j  Trees  thinned  from  302  to  the  acre  to  151.5  to  the  acre,  leaving  only  one-half  of  the  original  planting. 


BUL.  414]      PLANTING    DISTANCES   FOR   DECIDUOUS   FRUIT    TREES 


11 


/a  x  /e 

16  x  /6 

bo  »eo 

30  a  JO 
36  a  JO 

/e  a  te 

16  a  16 

ao  a  eo 

30  a  JO 


m 


(^    30. 


s 

/6  a 

.10 

QS 

eo 

/£a  /a 

16  a /6 

eoAeo 
a4*e4 

JO  A  JO 

f£*  /a 

/6  a  16 

eoAao 
eAxeA 

JO  A  JO 

J6aJ6 


55        Go      65 


\I9I9  I 


i5Zo- 


i i         i 

\/<9ee\'a3\e4  1^5  I 


|  -i9  \    i9so       usee  \'ej   \a4\es  I 

19/9  Yeo  \        i oee  \'^)\     1MH         1 


;y\  /gao    I       /oea        \\{     /gas       ~~| 


£oyal  Apricots 


m/g\<geo\     /pee       \^4]    /gas        |" 
\i9foX    /9ea        I'feri  /$a*~~  \/9as\ 


%  I II  jses    I 


19/9   \ao\    /see  '  \/ges\ 


Elberta  Peaches 


i9/g  I    /peo      \ 


rr 


1 7579  I 


\/gej  je4\/gas 


\/9)     /geo        \       /ge3        |  /9ej    \  0s\ 


\/9\    /geo  J       /gee         i       /gas       I  Wi         Climax    Plums 


1 '  z  \ 


\    /paj      \/9e/i  (  /ges  \ 


\\eo[  i9aa    \      /ge3        \'  )£S\ 


}/geo\      /gee  .      |/fe5| 


/peo  j   /gee     { /gas) 


\/9eo  { /gee  _  tas\ 


Pond    Plums 


ESH" 


dO\  1 19£5  I 


\/9£o  \az\'    /gaj  \as\ 


faoj  /gee  i~ 


/gas'  \ 


French   Prunes 


m 


/gas 


[{      /9aj         \~ /gas    |" 


V9  |  ao  |      /9aa 


I      /gaj 


\\   /gee     pQ;~ 

I  /  /gae      i  /gas '  \s£\ ) 

( /gas  \  /gaj   \  \/gas\  __ 


Bartlett    Pears 


\   /gea       I     /gej       yad  yes~\ 
Weal  /gaj  \a4\  '/ges~\' 

I I I I L 


to 


,'5 


eo       as       jo       35       4o 
Thousands  of   Pounds 


SO        65 


Fig.  3. — Average  annual  and  total  yields  of  trees  per  acre  under  different 
planting    distances. 


12  UNIVERSITY    OP    CALIFORNIA EXPERIMENT    STATION 

In  the  case  of  the  peach,  the  growth,  vigor,  and  fruiting  habits 
were  so  early  influenced  by  the  close  planting  that  the  trees  set  closer 
than  20  feet  produced  practically  nothing  except  during  1925  when 
only  two  remaining  alive  and  no  longer  crowded  produced  a  fair 
crop.  Trees  planted  24  and  30  feet  apart  have  produced  not  only 
greater  yields  per  tree  but  the  largest  tonnage  per  acre. 

With  the  apricot  the  general  results  were  similar  but  not  so 
marked.  A  large  acre  yield  was  produced  on  5-3^ear-old  trees  planted 
12  x  12  feet.  The  fruit,  however,  was  small  and  of  little  commercial 
value ;  during  the  subsequent  four  fruiting  seasons  the  trees  planted 
20  and  24  feet  gave  the  highest  yields.  While  it  is  speculative  to 
forecast  the  future,  there  are  reasons  for  believing  that  the  trees 
standing  at  30  and  36  feet  will,  during  the  next  five  years,  produce 
the  largest  total  yields  per  acre. 

French  prunes  have  likewise  failed  to  give  larger  yields  from  the 
very  closely  planted  trees  during  the  first  five  crop  years,  and  although 
the  20-foot  spacing  produced  a  crop  in  1923  which  to  date  gives  this 
spacing  the  highest  yield,  the  increase  in  production  of  the  24-foot 
planting  during  1925  indicates  that  this  distance  will  very  soon 
become  the  most  profitable.  The  30-foot  planting,  while  producing 
larger  yields  per  tree,  naturally  does  not  make  a  favorable  showing 
in  total  acre  yields  until  the  trees  reach  15  or  20  years  of  age. 

During  the  season  of  1925  yield  records  were  secured  from  an 
orchard  in  Napa  County  where  one  hundred  14-year-old  French 
prune  trees,  growing  30  feet  apart,  yielded  4.9  green  tons  per  acve 
as  compared  with  5.6  tons  from  a  similar  number  of  trees  30  years 
of  age  planted  only  18  feet  apart.  In  this  instance  where  only  48 
trees  per  acre  are  compared  with  100  per  acre,  the  difference  in  yields 
of  dried  fruit  was  not  great  and  the  size  of  the  fruit  in  the  former 
instance  ran  from  30  to  45  to  the  pound  as  compared  with  50  to  60 
to  the  pound  from  the  closer  planted  trees. 

Climax  and  Pond  plums,  both  naturally  smaller  growing  trees 
than  apricots,  peaches,  or  prunes,  undoubtedly  require  relatively  close 
planting  in  order  to  secure  large  tonnage. 

The  yields  from  the  Bartlett  trees  under  experiment  were  so  small 
as  to  make  definite  conclusions  unwarranted.  It  seems,  however,  that 
since  trees  planted  12  feet  apart  gave  practically  the  same  acre  yields 
as  those  planted  30  feet  apart  and  since  they  were  not  materially 
weakened  by  the  crowding,  this  fruit  is  adapted  to  rather  a  wide  range 
of  planting  distances.  Observations  in  commercial  orchards  also 
indicate  that  the  Bartlett  is  capable  of  adapting  itself  to  its  surround- 


BUL.  414]      PLANTING   DISTANCES    FOR   DECIDUOUS    FRUIT    TREES  13 

ings.  It  is  believed  that  this  conclusion  holds  true  with  the  pear 
generally,  although  little  information  is  available  on  any  other  variety. 
No  yields  have  been  secured  thus  far  from  the  cherries  under  test. 
Under  favorable  conditions,  however,  the  sweet  cherry  produces  a 
large  tree  and  hence  may  be  expected  to  give  good  yields  under  at 
least  moderately  wide  planting.  With  unrestricted  room  for  develop- 
ment, a  15-year-old  tree  in  the  orchard  of  Giblin  Brothers  of  Yuba 
City  in  1924  produced  1453  pounds  of  fruit  as  compared  with  an 
average  yield  of  532  pounds  from  trees  in  the  orchard  standing 
20  x  40  feet  apart. 


HARMFUL    EFFECTS    OF    CLOSE    PLANTING 

Mistakes  which  have  been  made  in  planting  have  been  almos# 
without  exception  those  of  planting  the  trees  too  close.  In  orchards 
planted  many  years  ago  this  was  a  mistake  very  easy  to  make.  New 
fruits  were  being  planted  in  different  sections  of  the  state  with  but 
little  definite  information  as  to  how  much  space  the  trees  would 
occupy  eventually.  Many  of  these  pioneer  orchards  and  occasionally 
some  planted  more  recently,  are  now  recognized  as  having  been  set 
too  close. 

Interlocking  of  the  branches  between  the  tree  rows  renders  culti- 
vation and  spraying  difficult.  At  harvest  time  when  the  branches  are 
bending  under  a  load  of  fruit,  picking  and  handling  the  crop  in  the 
orchard  is  exceedingly  difficult.  The  crowding  of  branches  and  the 
large  leaf  area  during  the  growing  season  also  produce  a  large  amount 
of  shade  which  may  prove  detrimental  by  preventing  proper  coloring 
of  the  fruit  or  by  actually  killing  off  or  preventing  the  formation 
of  new  fruit-buds  and  spurs?  While  a  certain  amount  of  sunlight  is 
necessary  in  order  to  carry  on  the  normal  wood  and  Jeaf  growth  of 
the  tree,  even  more  is  required  for  fruit-bud  formation.  This  seems 
most  striking  with  apricots  and  peaches  where  under  conditions  of 
limited  light  all  of  the  bruiting  area  is  found  on  the  uppermost 
branches. 

Yields  and  size  of  fruit  may  also  be  reduced  by  the  severe  compe- 
tition of  the  individual  trees  for  the  moisture  and  mineral  elements 
in  the  soil,  as  has  been  strikingly  set  forth  by  the  experiments  cited 
above. 


14  UNIVERSITY    OP    CALIFORNIA EXPERIMENT    STATION 


DOUBLE    PLANTING 

In  an  effort  to  secure  a  greater  income  from  the  trees  during  the 
first  few  crop  years,  the  idea  of  double  planting  is  often  carried  out. 
Occasionally  the  trees  and  tree  rows  are  planted  twice  as  close  together 
as  they  are  planned  to  stand  permanently,  but  more  often  the  quin- 
cunx system  of  planting  the  permanent  trees  in  a  square  with  a 
temporary  tree  in  the  center  of  each  is  used.  This  method,  if  well 
planned,  has  promising  possibilities  but  very  grave  dangers.  It  is 
believed  possible,  on  good  soil,  with  an  unlimited  water  supply,  and 
with  good  management,  to  make  the  temporary  trees — those  in  the 
center  of  the  square — more  than  pay  for  their  care,  thus  giving  some 
returns  which  would  otherwise  not  be  received.  If  at  the  time  of 
setting  the  orchard  one  is  undecided  as  to  which  of  two  fruits  or 
varieties  will  make  the  best  growth  or  prove  the  most  profitable  he 
may  find  double  planting  advantageous.  Not  infrequently  is  the  final 
decision  in  this  connection  postponed  until  after  the  trees  produce 
several  crops,  and  the  market  demands  are  established. 

Against  these  possibilities  is  the  danger  that  the  close  planting 
may  exert  a  dwarfing  effect  upon  the  trees  even  before  they  produce 
their  first  commercial  crop  and  if  allowed  to  remain  until  some  paying 
returns  can  be  secured,  permanent  damage  may  be  done. 

The  details  presented  in  figure  1,  of  trees  planted  from  12  to  36 
feet  apart,  show  how  early  the  tree  growth  was  checked  by  close 
planting.  Figures  4  to  8,  inclusive,  also  bring  out  more  forcibly  the 
comparative  size  and  condition  of  the  trees  at  the  time  of  and 
subsequent  to  thinning.  While  this  much  weakened  condition  was 
doubtless  exaggerated  by  an  insufficient  water  supply,  it  is  believed 
that  water  scarcity  is  also  the  limiting  factor  in  many  commercial 
orchards.  Figure  9  shows  just  such  a  condition  in  a  Napa  Valley 
orchard,  which  is  typical  of  similar  orchards  in  many  sections.  So 
long  as  all  the  trees  are  standing  in  their  crowded  condition,  the 
harmful  effects  of  such  planting  is  not  evident.  As  soon  as  the 
temporary  ones  are  removed,  however,  the  mistake  is  easy  to  see. 

As  mentioned  above,  perhaps  the  primary  purpose  of  double 
planting  is  to  secure  larger  returns.  How  successfully  does  such  a 
practice  work  out  in  commercial  orchards?  Since  comparative  yields 
are  not  available,  the  question  can  only  be  answered  by  giving  the 
opinions  of  orchardists  who  have  followed  this  system.  Trees  planted 
by  H.  G.  Boyce,  near  Winters,  in  1893,  24  feet  apart  on  the  square, 
were  thinned  by  removing  alternate  diagonal  rows  in  1913,  allowing 


BUL.  414]      PLANTING    DISTANCES    FOR    DECIDUOUS    FRUIT    TREES 


15 


my 


.--->•.:    ■ 


Fig.  4. — Eight-year-old  Elberta  peach  trees.  A,  two  years  after  thinning 
from  12  x  12  feet  to  24  x  24  feet.  Only  one  tree  out  of  four  of  any  value. 
B,  trees  planted  20  x  20  feet.  Half  of  the  trees  in  fair  condition,  others  very 
weak.  C,  trees  planted  24  x  24  feet.  All  in  good  condition.  Compare  with  trees 
in  A. 


16 


UNIVERSITY    OP    CALIFORNIA EXPERIMENT    STATION 


Fig.   5. — Eoyal   apricot   trees.      A, 
apart.      B,   same   trees   second   season   after   thinning   to    24  x  24   feet, 
parable  trees  planted  24  x  24  feet.     Compare  size  and  vigor. 


trees   six  years   old   standing   12  x  12   feet 

C,   com- 


BUL.  414]      PLANTING    DISTANCES    FOR    DECIDUOUS    FRUIT    TREES 


17 


the  remaining  trees  to  stand  48  x  48  feet  on  the  square  but  only  34 
feet  on  the  diagonal.  Though  the  branches  are  touching  in  the  close 
or  diagonal  direction,  the  trees  produce  large  crops.  An  additional 
20  acres  of  10-year-old  almonds  will  in  a  few  years  be  thinned  in  like 


Fig.  6. — Eight-year-old  Climax  plum  trees.  A,  trees  thinned  several  months 
before  photographing  from  12  x  12  feet  to  24  x  24  feet.  B,  trees  originally  planted 
24  x  24  feet.     Compare  size  and  vigor. 


manner.    Mr.  ~Boyce  is  of  the  opinion  that  he  would  in  all  probability 
plant  and  handle  another  orchard  in  the  same  way. 

Mr.  William  D.  McKenzie,   an  extensive  grower  of  prunes  and 
pears   at   Monticello,   believes   double    planting   to    be    an   economic 


18 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  7. — Eight-year-old  Boyal  Ann  cherry  trees.  A,  thinned  several  months 
previous  to  photographing  from  12  x  12  feet  to  24  x  24  feet.  B,  trees  planted 
20  x  20  feet.  C,  trees  planted  24  x  24  feet.  Note  comparative  size  of  the  trees 
planted  at  24  feet. 


BUL.  414]      PLANTING    DISTANCES    FOR    DECIDUOUS    FRUIT    TREES 


19 


Fig.  8. — Eight-year-old  French  prune  trees.  A,  trees  thinned  several  months 
before  photographing  from  12  x  12  feet  to  24  x  24  feet.  B;  trees  originally 
planted  24  x  24  feet.     Note  the  comparative  size  and  vigor. 


20 


UNIVERSITY    OP    CALIFORNIA EXPERIMENT    STATION 


advantage.  In  planting-  French  prunes,  he  would  consider  setting' 
the  trees  20  x  20  feet  on  the  square  with  the  idea  of  later  removing 
the  diagonal  rows. 

Mr.  E.  A.  Gammon,  pear  grower  at  Hood,  believes  peaches  and 
plums  might  well  be  planted  as  temporary  trees  between  pears  set 
18  x  18  feet  under  his  conditions  on  the  bottom  lands  of  the  Sacra- 
mento River. 


Fig.  9. — Twenty-year-old  prune  orchard  interplanted  with  peaches.  Peach 
trees,  of  which  the  one  in  the  center  foreground  is  the  first  of  the  row,  are  very 
weak,  with  little  fruiting  wood,  while  the  prune  trees  in  blossom  on  either  side 
have  not  had  proper  chance  for  their  best  development. 


Batchelor4  states,  in  connection  with  the  practice  of  double  planting 
walnuts  30  x  60  feet,  that  ' '  By  this  method  properly  carried  out, 
nearly  twice  the  tonnage  may  be  expected  during  the  first  10  to  14 
years,  as  where  only  the  permanent  trees  are  planted."  These  instances 
are  typical  of  the  views  of  many  orchardists. 

On  the  other  hand,  there  are  many  growers  who  condemn  the 
practice  on  the  ground  that  the  orchard  will  not  be  thinned  in  time 
and  that  the  extra  trees  will  not  materially  increase  the  returns.  This 
opinion  deserves  special  consideration  with  such  fruits  as  the  peach 
and  the  plum,  which  make  a  quick  growth  and  come  into  bearing 
early.  Double  planting  apple  orchards  does  not  seem  feasible  in  the 
leading  producing  districts  of  California  because  there  are  no  suitable 


4  Batchelor,  L.  D.     Walnut  culture  in  California.     Calif.  Agr.  Exp.  Sta.  Bui. 
379:38. 


BUL.  414]      PLANTING    DISTANCES    FOR    DECIDUOUS    FRUIT    TREES  21 

commercial  varieties  grown  which  will  give  profitable  returns  before 
the  trees  begin  to  crowd.  Moreover,  such  fruits  as  plums  or  peaches, 
which  might  be  suitable  for  this  purpose,  are  not  well  adapted  to 
the  apple  sections. 

Figure  10  shows  a  14-year-old  almond  orchard  where  the  trees  are 
planted  30  x  30  feet  apart  quincunx  system  with  peach  fillers.  Although 
the  size  of  the  trees  has  been  reduced  somewhat  by  crowding,  good 
care  and  plenty  of  water  have  up  to  this  time  maintained  sufficient 


Fig.    10. — Almond   orchard  with   peach   fillers.      Almond   trees    30  x  30    feet   with 

peach  trees  in  the  center. 

vigor  to  make  them  profitable.  Just  how  much  longer  they  can 
continue  to  produce  their  present  returns  under  such  conditions  is, 
however,  difficult  to  state. 

The  advisability  and  profitableness  of  the  practice  of  double 
planting,  therefore,  depends  primarily  upon  the  kinds  of  fruit  grown, 
the  difference  in  time  required  for  the  permanent  and  temporary  trees 
to  reach  good  bearing  age,  the  available  water  supply,  and  last,  but 
perhaps  most  important  of  all,  the  courage  of  the  grower  to  remove 
the  temporary  trees  at  the  proper  time. 

Thinning  old  orchards. — As  mentioned  previously,  many  of  the 
older  orchards,  planted  with  little  knowledge  of  how  the  trees  would 
grow  and  at  a  time  when  very  severe  pruning  was  generally  prac- 
ticed, are  now  badly  crowded.  Even  with  severe  heading  of  the  main 
limbs,  often  into  two-  and  three-year-old  wood,  cultivation  and  spray- 


22  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

ing  has  become  difficult,  and  with  the  branches  weighted  down  under  a 
load  of  fruit,  harvesting  is  much  more  of  a  task.  How  should  such 
orchards  be  treated?  Should  they  be  allowed  to  remain  as  they 
are  with  the  inconveniences  and  with  the  extra  expense  of  handling, 
or  should  part  of  the  trees  be  removed?  The  answer  to  these  ques- 
tions depends  almost  entirely  upon  the  individual  orchard  and  upon 
the  orchardist.  In  some  cases,  thinning  would  be  recommended 
without  hesitation.  In  others  it  would  be  considered  a  mistake,  par- 
ticularly where  thinning  has  been  delayed  until  all  the  trees  are 
permanently  injured.  With  the  peaches  and  apricots  planted  12  x  12 
feet  apart  on  the  University  Farm,  permanent  injury  occurred  before 
any  of  the  trees  were  removed,  although  to  have  thinned  the  trees 
much  sooner  would  have  meant  removing  them  before  any  returns 
had  been  received. 

Figure,  1,  showing  the  growth  of  apricots,  peaches,  and  plums, 
discloses  a  slight  gain  in  tree  size  in  the  plantings  during  the  seasons 
of  1922  and  1923,  but  figures  6,  7,  and  8  show  that  the  trees  were 
dwarfed,  and  in  the  case  of  the  peach  trees,  were  almost  killed  before 
thinning.  A  similar  condition  was  observed  in  an  old  apple  orchard 
in  Sonoma  County  where  the  trees,  long  standing  20  x  20  feet,  had 
been  thinned  several  years  previously  to  40  x  40  feet.  These  trees, 
receiving  only  the  natural  rainfall,  had  competed  with  each  other  for 
soil  moisture  so  long  as  to  make  any  material  increase  in  growth  after 
thinning  very  doubtful.  Moreover,  75  per  cent  of  the  trees  had 
been  removed  so  as  to  make  a  commercial  crop  practically  impossible. 

The  great  majority  of  mistakes,  however,  have  been  those  of  not 
thinning ;  a  few  specific  instances  of  successful  thinning  are  listed  in 
table  4. 

In  numerous  instances  in  Orange  County,  very  marked  increases  in 
walnut  yields  have  been  secured  the  third  or  fourth  year  after  the 
removal  of  half  the  trees  originally  planted  40  feet  apart. 

In  considering  the  time  and  method  of  thinning,  the  system  and 
distance  of  planting,  severity  of  crowding,  kind  and  age  of  trees, 
type  of  soil,  and  method  of  pruning  should  all  be  taken  into  consider- 
ation. The  system  and  distance  of  planting  determine  the  spacing 
and  number  of  trees  allowed  to  remain.  While  thinning  to  some 
extent  may  be  done  by  removing  only  a  few  miscellaneous  trees,  even 
distribution  can  be  secured  only  by  taking  out  from  50  to  75  per  cent 
of  the  original  planting  through  the  removal  of  alternate  rows  in  one 
or  both  directions,  either  on  the  square  or  diagonal.  The  summary 
and  diagrams  in  table  5  illustrate  the  different  methods  and  the  result 
of  each. 


BUL.  414]      PLANTING    DISTANCES   FOR   DECIDUOUS   FRUIT    TREES 


23 


TABLE  4 
Results   of  Orchard  Thinning 


Fruit 

Planted 

Thinned 

Orchard 

When 

How 

When 

How 

Results 

E.  A.  Gammon,  Hood 

Pears 

1890 

16  x  16 

1915 

22.5  x  32 

Better   trees  and   fruit   and 

Wm.  McKenzie,  Monticello 

Prunes 

1890 

20x20 

1917 

28x28 

larger  yields. 
Larger  and  better  fruit  and 

Henry  Wheatley,  Napa 

Prunes 

1900 

18x18 

1915 

18x36 

greater  yields. 
Much     larger     trees.     Com- 

parative    yields,     thinned 
and  unthinned  trees,  1925, 

the  same,   but  more  fruit 

of    good    size    on    thinned 

trees. 

H.  G.  Boyce,  Winters 

Apricots 

1893 

24x24 

1913 

34x48 

Trees   using  all   the   34-foot 

H.  G.  Boyce,  Winters 

Almonds 

1883 

24x24 

1913 

34x48 

space.     Large  crops. 
Large  crops. 

W.   D.   Wilkins,   Mountain 
View. 

Apricots 

1898 

22x22 

1910 

22x44 

Large      trees      with      heavy 
yields. 

Limoneira    Ranch,    Santa 

Walnuts 

1891 

40x40 

1916 

40x80 

No    increase    in    yields    for 

Paula. 

several   years   previous   to 
thinning.          Yields     now 
doubled. 

TABLE  5 

Systems  of  Thinning 


System  of 
planting 

Method  of  thinning 

Reduc- 
tion in 
number 
of  trees 

Form  of 
planting 

after 
thinning 

Remarks 

Square 

50% 

Rectangular 

Relieves  crowding  only  in  one 
direction. 

Alternate  rows  both  direc- 

75% 

Square 

Usually  too  severe.    Too  few 

tions. 

trees  left. 

Alternate  diagonal  rows  or 

50% 

Quincunx 

Most    common    method.     Re- 

alternate trees  in  each  row. 

maining  trees  well  spaced. 

50% 

Square 

Trees  quickly  crowd  in  one 
direction. 

Quincunx 

Alternate  rows  or  removal  of 
tree  in  center  of  square. 

50% 

Square 

planting  to  secure  even  dis- 

tribution. 

Hexagonal 

Alternate  trees  in  alternate 
rows  or  tree  in  center  of 
hexagon. 

25% 

Hexagonal 

Thinning  too  light  to  be  of 
great  value. 

Hexagonal  or 

Alternate  tree  in  each  row  or 

50% 

Irregular     di- 

Relieves crowding  only  in  one 

triangular. 

alternate  diagonal  rows. 

agonal. 

direction. 

Alternate  rows  either  on  the 

75% 

Square  or  tri- 

Very  satisfactory    with    large, 

square  or  diagonal  and  al- 

angular. 

thrifty,       long-lived       trees 

ternate  tree  in  remaining 

which       will       satisfactorily 

row. 

utilize  the  space.  With 
smaller,  weaker  trees,  the 
thinning  is  too  severe. 

24 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


J: 

O       J 

&—9     ■ 

T    ° 

0                0 

or     o 

3               O 

>t      o 

>:      o 

»t     o      J« 

(a)    Removal    of    alternate 
rows. 


Square  Planting 

(b)    Removal    of    alternate 
rows   in   both   directions. 


(c)    Removal    of    alternate 
diagonal   rows. 


Rectangular 

(d)     Removal   of   alternate 
rows. 


(u)    Removal   of    alternate 
diagonal   rows. 


6     % 

o 

o      o 

o 

o      o 

o 

o       o 

0 

0 

o 

o 

-  -  -  - 

6 

- '  -  -  < 

o 
o 
o 

--P 

1-6 

3 

o 
o 
o 

o 
o 
o 
o 

o 
o 

0 

o 
o 

Quincunx 
(e)    Removal    of    alternate 


Hexagonal 
(f)    Removal    of    alternate 


rows    or    the    center    tree    of      rows   in   either  of   two   direc- 
tions. 


each    square. 


S^ 


it 


f=^ 


<®JE 


9 


V 


31      o 


Triangular 

(h)    Removal    of    alternate  (i)     Removal    of    alternate 

rows    and   each    even   tree    in  rows    and    each    odd    tree    in 

the  remaining  rows.  the  remaining  rows. 


Fig.  11. — Systems  of  planting  and  methods  of  thinning. 


In  figure  11  a  uniform  distance  of  25  feet  has  been  used  as 
illustrative  of  the  fact  that  although  the  systems  of  thinning  have 
considerable  similarity,  they  differ  in  the  amount  of  space  allowed 
each  tree.  Since  it  is  often  desirable  to  know  the  diagonal  spacing 
between  trees  planted  at  different  distances  and  according  to  the 
different  systems,  a  few  of  these  distances  have  been  calculated.  They 
are  shown  in  table  6. 


BUL.  414]      PLANTING    DISTANCES    FOR    DECIDUOUS    FRUIT    TREES 


25 


TABLE  <3 
Diagonal  Distances  Between  Trees 


Distances  on  the  diagonal 

Distances  of 
planting 

(1) 

Square 
planting 

(2) 

Alternate 
planting 
(3) 

Quincunx  planting 

(4) 

Hexagonal  planting 

(5) 

18  x  18 

25.5 

20  1 

20x20 

28.3 

22.4 

22x22 

31.1 

24.6 

25  x  25 

35.3 

27.9 

27x27 

38.2 

30.2 

One-half  the  distances  given 

All  trees  equidistant.     Same  as 

30  x  30 

42  5 

33.5 

in  column  2. 

column  1. 

35  x  35 

49.5 

39.1 

40x40 

56.6 

44.8 

50x50 

70.7 

55.9 

60  x  60 

84.9 

67  1 

Where  one  has  a  choice  of  two  methods,  the  one  best  adapted  to 
the  trees'  needs  should  be  chosen.  If  crowding  and  severe  pruning 
has  been  necessary  to  keep  the  trees  within  bounds,  the  wider  spacing 
should  be  chosen.  If,  on  the  other  hand,  the  trees  are  on  thin  soil, 
have  never  been  very  vigorous,  and  have  attained  practically  their 
full  size,  thinning  should  be  done  lightly.  It  is  in  this  connection  that 
the  orchardist  must  rely  upon  his  good  judgment  as  to  how  many 
trees  should  be  removed.  An  effort  must  be  made  to  forecast  the 
probable  response  of  the  trees  to  the  thinning.  As  a  rule  this  is  not 
extremely  difficult  when  the  factors  influencing  the  growth  of  the 
trees  are  considered.  Vigorously  growing  trees  with  branches  inter- 
lacing clearly  need  more  room  for  their  development.  Mature  or 
old  bearing  trees  making  little  new  wood  growth  each  year  may 
or  may  not  respond  to  a  wider  spacing,  depending  upon  the  factors 
mentioned  above.  While  such  trees  may  have  had  their  vigor  checked 
by  crowding,  beneficial  results  from  thinning  can  probably  be  secured 
only  by  encouraging  more  wood  growth  through  a  heavier  pruning, 
an  increased  soil  moisture  supply,  or  perhaps  by  the  addition  of 
organic  or  nitrogenous  fertilizers.  In  other  words,  crowding  has  been 
only  one  factor  limiting  their  growth,  and  if  better  orchard  manage- 
ment generally  does  not  accompany  thinning,  removing  a  portion  of 
the  trees  will  only  result  in  loss.  While  old  trees  may  be  rejuvenated 
after  thinning,  much  better  results  can  be  expected  by  removing  the 
crowding  trees  as  soon  as  it  is  evident  that  such  a  condition  exists. 
As  pointed  out  in  connection  with  double  planting,  thinning  is  usually 
delayed  too  long.  For  best  results,  it  must  be  done  before  and  not 
after  the  trees  become  weakened.     This  means  that  the  grower  must 


26  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

have  courage  to  cut  out  approximately  half  of  his  trees  just  at  the 
time  when  they  are  in  prime  condition.  Such  a  practice  cannot  but 
result  in  a  financial  loss  for  two  or  three  years,  but  where  thinning  is 
justifiable,  it  will  likewise  result  in  a  larger  crop  of  better  fruit  during 
the  future  life  of  the  orchard.  It  is  to  be  decided,  therefore,  whether 
it  is  more  desirable  to  secure  the  maximum  returns  over  a  relatively 
few  years  or  have  the  yields  gradually  increase  over  a  long  period  of 
time.  In  order  to  permit  the  removal  of  bearing  trees  with  the  least 
financial  sacrifice,  it  is  suggested  that  severe  pruning  be  practiced  on 
the  trees  which  are  to  be  removed  for  two  or  three  seasons  previous 
to  thinning.  This  would  allow  for  some  crop  returns  and  at  the 
same  time  would  permit  expansion  of  the  trees  which  are  to  remain. 
It  should  be  pointed  out  in  this  connection,  however,  that  the  roots 
of  the  trees  are  still  competing  with  each  other  for  the  moisture  and 
plant  food  materials  in  the  soil,  and  that  unless  these  are  present  in 
large  amounts,  the  yields  will  not  be  as  good  as  when  the  entire  tree 
is  removed.     Such  a  practice  is  only  a  temporary  expedient. 

SUGGESTIONS    FOR    NEW    PLANTINGS 

It  should  be  evident  that  definite  planting  distances  can  be  intelli- 
gently determined  only  by  the  individual  grower  who  takes  into  con- 
sideration his  soil,  the  habits  of  the  fruit  or  variety  in  question,  and 
the  proposed  method  of  handling  his  trees.  However,  the  following 
suggestions,  based  upon  results  of  the  above  experiments  and  the 
experience  of  the  most  successful  growers,  are  offered  as  being  of 
possible  assistance  to  prospective  planters. 

Almonds. — An  extensive  survey  of  the  almond  industry  of  the 
state  by  Mr.  M.  N.  Wood  of  the  United  States  Department  of  Agri- 
culture reveals  the  fact  that  planting  distances  vary  from  16  to  35 
feet,  the  majority  of  trees  being  set  at  an  intermediate  distance  of 
approximately  25  feet.  Few  new  orchards  can  be  found  where  the 
trees  are  planted  closer  than  24  to  26  feet,  and  on  the  better  types 
of  soils  where  the  trees  are  to  have  good  care,  and  sufficient  irrigation 
facilities,  30  feet  is  recommended.  Exceptionally  large  individual 
trees  have  been  found,  one  near  Chico  having  a  spread  of  branches  of 
forty-seven  feet. 

Apples. — Thirty  by  thirty  feet  has  long  been  more  or  less  of  a 
standard  planting  distance  in  many  apple  sections  of  the  United 
States.  The  majority  of  plantings  in  California,  however,  have  been 
somewhat  closer,  although  extreme  crowding  of  the  apple  has  not 
been  so  prevalent  as  has  been  the  case  with  the  other  deciduous  fruits. 


BUL.  414]      PLANTING   DISTANCES    FOR   DECIDUOUS   FRUIT    TREES  27 

In  most  of  the  earlier  plantings  in  the  Watsonville  district  the  trees 
were  set  24  to  26  feet  apart,  while  in  the  Sebastopol  district  most 
of  the  plantings  are  from  20  to  24  feet.  These  distances,  especially 
for  the  leading  variety,  the  Gravenstein,  have  proved  too  close. 

Except  for  small  upright  growing  varieties,  such  as  Eome  Beauty, 
it  is  generally  undesirable  that  the  trees  be  planted  closer  than  30  feet 
apart.  On  the  other  hand,  many  varieties  on  good  soil  and  under 
favorable  conditions  will  easily  utilize  35  feet  with  advantage.  Partic- 
ularly is  this  true  in  coastal  sections  subject  to  fog  where  the  trees  and 
ripening  fruit  should  be  allowed  the  maximum  sunlight  obtainable. 

Apricots.— While  many  apricot  orchards  in  the  leading  districts 
are  planted  with  the  trees  at  a  distance  of  from  20  to  22  feet  apart, 
newer  plantings  are  made  at  a  distance  from  24  feet  as  a  minimum 
to  35  feet  as  a  maximum.  On  deep  soil  with  plenty  of  water,  26  to  30 
feet  is  recommended.  The  apricot  generally  is  one  of  the  larger 
growing  fruit  trees,  and  with  a  moderate  system  of  pruning,  most 
varieties,  particularly  the  Moorpark,  should  be  given  plenty  of  room 
for  development. 

Cherries. — Although  sweet  cherry  trees  are  characterized  by  an 
upright  habit  of  growth,  they  also  attain  large  size  under  ideal 
conditions.  Twenty-four  feet  is  suggested  as  a  minimum  distance 
with  from  26  to  30  feet  as  an  optimum  distance  on  fertile,  moist,  but 
well  drained  soils.  As  mentioned  previously,  individual  trees  have  been 
noted  in  Sutter  County  which  occupied  35  to  40  feet  to  advantage. 

Peaches. — Distances  for  planting  peaches  vary  widely.  In  the 
peach  sections  of  Placer  County  where  many  of  the  orchards  are 
on  comparatively  shallow  or  thin  soil,  most  of  the  present  plantings 
are  either  16  or  18  feet,  and  until  more  growth  can  be  secured  by 
additional  water,  fertility,  or  other  means,  it  is  doubtful  if  a  distance 
greater  than  20  feet  is  justifiable. 

In  the  producing  sections  of  the  San  Joaquin  and  Sacramento 
valleys,  many  orchards,  including  the  high  yielding  Brandstadt 
Orchard  at  Yuba  City,  are  planted  20  feet  apart.  This  distance, 
however,  is  believed  even  by  the  growers  of  that  section  to  be  too 
close  for  continued  high  yields.  From  22  to  24  feet  is  regarded  as 
more  desirable.  In  many  of  the  newer  orchards  now  being  planted, 
24  feet  is  considered  a  minimum.  Twenty-four  to  thirty  feet  is 
suggested  by  one  of  the  leading  nurserymen,  and  from  the  results  of 
the  experiments  reported  in  this  bulletin,  the  greater  distance  may 
frequently  be  used  with  advantage,  even  though  bearing  peach  trees 
should  be  given  a  somewhat  more  severe  pruning  than  the  other 
deciduous  fruits. 


28  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Pears. — The  pear  tree  seems  peculiarly  able  to  adapt  itself  to  its 
environment.  As  pointed  out,  the  trees  in  the  experimental  plots 
on  the  University  Farm  have  maintained  practically  a  healthy  con- 
dition and  fair  vigor  under  the  very  close  planting  of  12  x  12  feet. 
Other  trees  in  the  same  plots  and  also  in  other  orchards  have  utilized 
a  30-foot  spacing.  Recommendations  of  from  25  to  30  feet  are  now 
quite  common,  but  since  moderate  crowding  at  least  does  not  seem 
detrimental,  the  25-foot  planting  as  a  general  maximum  seems  best 
for  Bartletts.  The  majority  of  bearing  orchards  at  present  were 
planted  between  20  and  24  feet.  The  trees  are  not  large  but  do  well 
at  this  distance.  Pears  in  the  Sierra  foothills  should  naturally  be 
planted  closer  than  in  the  valley  or  river  sections. 

Plums  and  prunes. — Since  most  varieties  of  shipping  plums  are  of 
Japanese  origin  or  hybrids  of  Prunus  salicina  stock,  few  make  large 
trees,  perhaps  partly  because  of  the  inherent  nature  of  the  variety 
itself  and  partly  because  some  of  the  leading  plum  sections  do  not 
have  the  deepest  or  most  fertile  soil.  Eighteen  to  20  feet  is  the 
distance  usually  accepted  for  planting  in  most  districts.  Some  plant- 
ings in  the  Sierra  foothills  are  as  close  as  16  feet,  while  the  experiments 
under  soil  conditions  at  Davis  indicate  that  22  to  24  feet  should  be 
the  minimum. 

The  European  or  domestica  type  of  plums,  to  which  the  prunes 
belong,  produces  a  tree  of  considerably  greater  size  and  for  the  most 
part  is  grown  commercially  in  sections  favorable  for  good  tree  devel- 
opment. While  a  number  of  the  older  French  prune  orchards, 
particularly  in  Napa  and  Santa  Clara  Counties,  were  planted  18  and 
20  feet  apart,  this  distance  can  now  be  recommended  only  for  very 
thin  or  poor  soils.  Some  of  the  newer  plantings  are  being  set  as  far 
as  30  feet.  Between  these  extremes,  22  to  26  feet  is  the  most  common 
average.  On  deep  fertile  soils  25  feet  is  suggested  as  a  minimum 
distance. 

Walnuts. — Following  the  very  beneficial  results  of  the  walnut 
growers  of  Orange  County  in  thinning  their  groves,  60  feet  is  the 
distance  most  frequently  recommended  at  which  trees  should  stand 
after  about  10  to  12  years.  The  majority,  however,  favor  double 
planting  either  30  x  60  or  60  x  60  quincunx  system  and  removing  the 
surplus  trees  when  they  begin  to  crowd. 

In  some  of  the  non-irrigated  sections  of  northern  California  where 
the  trees  do  not  attain  such  large  size,  45  to  50  feet  is  felt  to  be  the 
most  profitable  distance  for  the  permanent  trees.  Almonds  or  peaches 
are  frequently  used  as  fillers  during  the  first  eight  or  ten  years  of 
the  life  of  the  orchard. 


BUL.  414]      PLANTING    DISTANCES    FOR    DECIDUOUS    FRUIT    TREES  29 


SUMMARY 

Close  planting  for  the  fruit  or  variety  concerned  is  recommended 
(a)  where  the  trees  naturally  fail  to  attain  large  size;  (b)  where 
small  trees  are  desired  and  heavy  pruning  is  practiced  annually ;  and 
(c)  where  it  is  the  desire  to  secure  the  greatest  returns  from  the 
orchard  during  the  first  few  crop  years  rather  than  the  maximum 
average  returns  over  a  considerably  longer  period. 

Close  planting  with  the  idea  of  thinning  out  a  portion  of  the 
trees  is  aptly  summed  up  by  one  grower  who  states,  "All  is  well  with 
close  planting,  if  the  trees  are  thinned  before  the  branches  and  root 
systems  begin  to  compete  for  space,  but  observation  tells  you  most 
growers  delay  this  far  too  long. ' ' 

The  desirability  of  relatively  wide  planting  is  becoming  more 
clearly  recognized  with  almost  all  deciduous  fruits  grown  under 
favorable  soil  and  moisture  conditions  and  under  a  moderate  system 
of  pruning.  While  something  is  sacrificed  in  the  size  of  the  first  few 
crops,  the  yields  tend  to  increase  steadily,  the  orchard  continues  to 
produce  better  quality  and  more  consistent  yields  over  a  greater  length 
of  time. 


ACKNOWLEDGMENTS 

The  writer  herewith  wishes  to  express  his  appreciation  to  Messrs. 
M.  W.  Dula,  Robt.  M.  Peckham,  and  Henry  Sevier,  past  and  present 
Orchardists,  and  to  Mr.  Lloyd  Austin,  former  Assistant  in  Pomology, 
for  assistance  in  securing  growth  measurements  and  yield  data 
annually ;  to  Miss  Edna  Russ  for  assistance  in  the  keeping  of  records 
and  for  photographic  work.  Much  gratitude  is  due  numerous  fruit 
growers  interviewed  and  to  Farm  Advisors  and  Horticultural  Com- 
missioners, who  willingly  gave  of  their  time  in  connection  with  this 
study. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 


No. 

253.   Irrigation   and   Soil   Conditions  in  the 
Sierra   Nevada   Foothills,    California. 

261.  Melaxuma    of    the    Walnut,     "Juglans 

regia." 

262.  Citrus   Diseases  of   Florida   and   Cuba 

Compared  with  Those  of  California. 

263.  Size   Grades   for  Ripe   Olives. 

268.   Growing  and  Grafting  Olive  Seedlings. 
273.   Preliminary  Report  on  Kearney  Vine- 
yard  Experimental    Drain. 

275.  The     Cultivation     of     Belladonna     in 

California. 

276.  The  Pomegranate. 

277.  Sudan    Grass. 

278.  Grain    Sorghums. 

279.  Irrigation   of   Rice   in    California. 
283.  The  Olive  Insects  of  California. 
294.   Bean   Culture  in   California. 

304.   A   Study  of  the  Effects  of  Freezes  on 

Citrus    in    California. 
310.   Plum    Pollination. 

312.  Mariout  Barley. 

313.  Pruning      Young      Deciduous       Fruit 

Trees. 
319.   Caprifigs    and    Caprification. 

324.  Storage  of   Perishable   Fruit   at  Freez- 

ing Temperatures. 

325.  Rice     Irrigation     Measurements      and 

Experiments    in    Sacramento    Valley, 

1914-1919. 
328.   Prune   Growing   in    California. 
331.   Phylloxera-Resistant    Stocks. 
335.   Cocoanut    Meal    as    a    Feed    for    Dairy 

Cows   and    Other   Livestock. 

339.  The    Relative    Cost    of    Making    Logs 

from    Small   and   Large  Timber. 

340.  Control     of     the     Pocket     Gopher     in 

California. 

343.  Cheese    Pests    and    Their    Control. 

344.  Cold    Storage   as   an    Aid   to   the   Mar- 

keting of  Plums. 

346.  Almond    Pollination. 

347.  The  Control  of  Red  Spiders  in  Decid- 

uous Orchards. 

348.  Pruning  Young  Olive  Trees. 

349.  A     Study    of    Sidedraft    and    Tractor 

Hitches. 

350.  Agriculture      in      Cut-over      Redwood 

Lands. 

352.  Further  Experiments  in  Plum  Pollina- 

tion. 

353.  Bovine   Infectious   Abortion. 

354.  Results  of  Rice  Experiments  in    1922. 

357.  A     Self-mixing    Dusting    Machine    for 

Applying      Dry       Insecticides       and 
Fungicides. 

358.  Black    Measles,     Water    Berries,     and 

Related  Vine  Troubles. 

361.  Preliminary    Yield    Tables    for    Second 

Growth   Redwood. 

362.  Dust   and   the  Tractor   Engine. 

363.  The  Pruning  of  Citrus  Trees  in   Cali- 

fornia. 

364.  Fungicidal    Dusts    for    the    Control    of 

Bunt. 

365.  Avocado  Culture  in   California. 

366.  Turkish  Tobacco  Culture,   Curing  and 

Marketing. 

367.  Methods  of  Harvesting  and  Irrigation 

in   Relation   of  Mouldy  Walnuts. 

368.  Bacterial  Decomposition  of  Olives  dur- 

ing Pickling. 

369.  Comparison     of     Woods     for     Butter 

Boxes. 


BULLETINS 
No. 


370. 
371. 


372. 


373. 
374. 


376. 

377. 
379. 
380. 

381. 

382. 

383. 

385. 
386. 

387. 
388. 

389. 
390. 

391. 

392. 
393. 
394. 

395. 

396. 

397. 

398. 
399. 


400. 
401. 

402. 
403. 
404. 
405. 
406. 
407. 


408. 
409. 


410. 
411. 


413. 
414, 


Browning  ot  Yellow  Newtown  Apples. 

The  Relative  Cost  of  Yarding  Small 
and   Large   Timber. 

The  Cost  of  Producing  Market  Milk  and 
Butterfat  on  246  California  Dairies. 

Pear    Pollination. 

A  Survey  of  Orchard  Practices  in  the 
Citrus  Industry  of  Southern  Cali- 
fornia. 

Results  of  Rice  Experiments  at  Cor- 
tena,    1923. 

Sun-Drying  and  Dehydration  of  Wal- 
nuts. 

The   Cold    Storage  of   Pears. 

Walnut   Culture   in   California. 

Growth  of  Eucalyptus  in  California 
Plantations. 

Growing  and  Handling  Asparagus 
Crowns. 

Pumping  for  Drainage  in  the  San 
Joaquin    Valley,    California. 

Monilia  Blossom  Blight  (Brown  Rot) 
of  Apricot. 

Pollination    of    the    Sweet    Cherry. 

Pruning  Bearing  Deciduous  Fruit 
Trees. 

Fig  Smut. 

The  Principles  and  Practice  of  Sun- 
drying  Fruit. 

Berseem  or   Egyptian    Clover. 

Harvesting  and  Packing  Grapes  in 
California. 

Machines  for  Coating  Seed  Wheat  with 
Copper    Carbonate    Dust. 

Fruit    Juice    Concentrates. 

Crop  Sequences  at  Davis. 

Cereal  Hay  Production  in  California. 
Feeding  Trials  with  Cereal  Hay. 

Bark   Diseases   of   Citrus  Trees. 

The  Mat  Bean  (Phaseolus  aeonitifo- 
lius). 

Manufacture  of  Roquefort  Type  Cheese 
from    Goat's   Milk. 

Orchard  Heating  in  California. 

The  Blackberry  Mite,  the  Cause  of 
Redberry  Disease  of  the  Himalaya 
Blackberry,    and    its    Control. 

The  Utilization  of  Surplus  Plums. 

Cost  of  Work  Horses  on  California 
Farms. 

The  Codling  Moth  in  Walnuts. 

Farm-Accounting  Associations. 

The  Dehydration  of  Prunes. 

Citrus  Culture  in  Central  California. 

Stationary  Spray  Plants  in  California. 

Yield,  Stand  and  Volume  Tables  for 
White  Fir  in  the  California  Pine 
Region. 

Alternaria  Rot  of  Lemons. 

The  Digestibility  of  Certain  Fruit  By- 
products as  Determined  for  Rumi- 
nants. 

Factors  Affecting  the  Quality  of  Fresh 
Asparagus  after  it  is  Harvested. 

Paradichlorobenzene  as  a  Soil  Fumi- 
gant. 

A  Study  of  the  Relative  Values  of  Cer- 
tain Root  Crops  and  Salmon  Oil  as 
Sources  of  Vitamin  A  for  Poultry. 

The  California  Poultry  Industry;  a 
Statistical   Study. 

Planting  and  Thinning  Distances  for 
Deciduous  Fruit  Trees. 


No. 

87. 
117. 

127. 
129. 
136. 

144. 

157. 
160. 
164. 
166. 
170. 

173. 

178. 
179. 

190. 
199. 
202. 

203. 
209. 
210. 
212. 
215. 
217. 

220. 
228. 
230. 

231. 
232. 

234. 

235. 

236. 


237. 

238. 
239. 

240. 

241. 

243. 

244. 
245. 
247. 
248. 

249. 
250. 

252. 
253. 
254. 


Alfalfa. 

The    Selection    and    Cost    of    a    Small 

Pumping   Plant. 
House    Fumigation. 
The  Control  of  Citrus   Insects. 
Melilotus    indica    as    a    Green-Manure 

Crop  for  California. 
Oidium    or    Powdery    Mildew    of    the 

Vine. 
Control  of  the  Pear  Scab. 
Lettuce  Growing  in  California. 
Smali  Fruit  Culture  in   California. 
The   County   Farm  Bureau. 
Fertilizing     California     Soils     for     the 

1918   Crop. 
The    Construction    of    the    Wood-Hoop 

Silo. 
The   Packing  of  Apples   in   California. 
Factors    of    Importance    in    Producing 

Milk  of  Low   Bacterial   Count. 
Agriculture  Clubs  in  California. 
Onion    Growing   in    California. 
County    Organizations   for   Rural    Fire 

Control. 
Peat   as    a   Manure    Substitute. 
The  Function  of  the  Farm  Bureau. 
Suggestions  to  the  Settler  in  California. 
Salvaging    Rain-Damaged    Prunes. 
Feeding  Dairy  Cows  in  California. 
Methods    for   Marketing  Vegetables   in 

California. 
Unfermented    Fruit   Juices. 
Vineyard   Irrigation  in  Arid  Climates. 
Testing  Milk,    Cream,    and   Skim   Milk 

for  Butterfat. 
The    Home    Vineyard. 
Harvesting    and    Handling    California 

Cherries    for    Eastern    Shipment. 
Winter  Injury  to  Young  Walnut  Trees 

during  1921-22. 
Soil     Analysis     and     Soil     and     Plant 

Inter-relations. 
The     Common     Hawks     and     Owls    of 

California    from    the    Standpoint    of 

the  Rancher. 
Directions  for  the  Tanning  and  Dress- 
ing of  Furs. 
The  Apricot  in   California. 
Harvesting     and     Handling     Apricots 

and  Plums  for  Eastern  Shipment. 
Harvesting    and    Handling    Pears    for 

Eastern   Shipment. 
Harvesting  and  Handling  Peaches  for 

Eastern   Shipment. 
Marmalade  Juice  and  Jelly  Juice  from 

Citrus  Fruits. 
Central  Wire  Bracing  for  Fruit  Trees. 
Vine   Pruning   Systems. 
Colonization    and    Rural    Development. 
Some    Common    Errors    in    Vine  Prun- 
ing and  Their  Remedies. 
Replacing    Missing    Vines. 
Measurement   of    Irrigation   Water   on 

the  Farm. 
Supports  for  Vines. 
Vineyard  Plans. 
The  Use  of  Artificial  Light  to  Increase 

Winter   Egg   Production. 


CIRCULARS 
No. 

255. 


256. 
257. 
258. 
259. 
261. 
262. 
263. 
264. 

265. 
266. 


269. 
270. 
272. 

273. 

274. 

276. 

277. 

278. 
279. 
281. 

282. 

283. 
284. 
285. 
286. 
287. 
288. 
289. 
290. 
291. 

292. 
293. 
294. 
295. 


298. 

299. 
300. 
301. 
302. 
303. 

304. 
305. 
306. 

307. 
308. 


Leguminous  Plants  as  Organic  Fertil- 
izer   in    California    Agriculture. 

The   Control   of  Wild   Morning   Glory. 

The  Small-Seeded  Horse  Bean. 

Thinning   Deciduous    Fruits. 

Pear  By-products. 

Sewing  Grain  Sacks. 

Cabbage  Growing  in   California. 

Tomato  Production  in   California. 

Preliminary  Essentials  to  Bovine 
Tuberculosis  Control. 

Plant   Disease   and   Pest   Control. 

Analyzing  the  Citrus  Orchard  by 
Means   of    Simple   Tree   Records. 

The  Tendency  of  Tractors  to  Rise  in 
Front;    Causes   and   Remedies. 

An  Orchard  Brush  Burner. 

A  Farm   Septic  Tank. 

California  Farm  Tenancy  and  Methods 
of  Leasing. 

Saving  the   Gophered  Citrus  Tree. 

Fusarium  Wilt  of  Tomato  and  its  Con- 
trol by  Means  of  Resistant  Varieties. 

Home  Canning. 

Head,  Cane,  and  Cordon  Pruning  of 
Vines. 

Olive  Pickling  in  Mediterranean  Coun- 
tries. 

The  Preparation  and  Refining  of  Olive 
Oil   in    Southern    Europe. 

The  Results  of  a  Survey  to  Determine 
the  Cost  of  Producing  Beef  in  Cali- 
fornia. 

Prevention  of  Insect  Attack  on  Stored 
Grain. 

Fertilizing  Citrus  Trees  in  California. 

The   Almond   in   California. 

Sweet  Potato  Production  in  California. 

Milk  Houses  for  California  Dairies. 

Potato    Production   in   California. 

Phylloxera   Resistant  Vineyards. 

Oak  Fungus  in  Orchard  Trees. 

The  Tangier  Pea. 

Blackhead  and  Other  Causes  of  Loss 
of  Turkeys  in   California. 

Alkali   Soils. 

The    Basis    of   Grape    Standardization. 

Propagation    of   Deciduous   Fruits. 

The  Growing  and  Handling  of  Head 
Lettuce  in   California. 

Control  of  the  California  Ground 
Squirrel. 

The  Possibilities  and  Limitations  of 
Cooperative   Marketing. 

Poultry   Breeding   Records. 

Coccidiosis  of  Chickens. 

Buckeye  Poisoning  of  the  Honey  Bee. 

The   Sugar  Beet   in   California. 

A  Promising  Remedy  for  Black  Measles 
of  the  Vine. 

Drainage  on   the  Farm. 

Liming  the  Soil. 

A  General  Purpose  Soil  Auger  and  its 
Use  on  the  Farm. 

American    Foulbrood    and  its   Control. 

Cantaloupe  Production  in  California. 


The  publications  listed  above  may  be  had  by  addressing 

College  of  Agriculture, 

University  of  California, 

Berkeley,  California. 

12m-ll,'26 


